In the renin-angiotensin system, peptides relating to coronary vessels and electrolyte homeostasis are produced by the enzymatic peptide-degradation cascade. In the cascade, angiotensinogen is first converted by renin into physiologically inert angiotensin I, angiotensin II, angiotensin III and finally into angiotensin IV which is a hexapeptide, successively. Angiotensin IV receptor is known to be distributed at high concentration in various organs such as brain (in particular, hippocampus), adrenal gland, heart, kidney, smooth muscle cells and endothelial cells. It is also reported that angiotensin IV relates to various physiological functions such as acceleration of renal blood flow (Swanson et al., Regulatory Peptides, 1992, 40, 409), cerebral vasodilation (Haberl et al., Circ. Res., 1991, 68, 1621), inhibition of cell proliferation (Barker and Aceto, Am. J. Physio., 1990, 259, H610) and hypermnesia (Miller-Wing, et al., J. Pharmacol. Exp. Thr., 1993, 266, 1718).
On the other hand, some peptide compounds are reported to act on angiotensin IV receptor agonistically (Sardinia, et al., Peptides, 1993, 14, 949; ibid., 1994, 8, 1399). However, these peptides should be composed of at least 5 amino acids to express high activities and have some problems in safety and the like. The amino compounds of the present invention have not been known.